Interface SocketOptions

Interface of methods to get/set socket options. This interface is
implemented by: SocketImpl and DatagramSocketImpl.
Subclasses of these should override the methods
of this interface in order to support their own options.

The methods and constants which specify options in this interface are
for implementation only. If you're not subclassing SocketImpl or
DatagramSocketImpl, you won't use these directly. There are
type-safe methods to get/set each of these options in Socket, ServerSocket,
DatagramSocket and MulticastSocket.

When the keepalive option is set for a TCP socket and no data
has been exchanged across the socket in either direction for
2 hours (NOTE: the actual value is implementation dependent),
TCP automatically sends a keepalive probe to the peer.

SO_BINDADDR

Fetch the local address binding of a socket (this option cannot
be "set" only "gotten", since sockets are bound at creation time,
and so the locally bound address cannot be changed). The default local
address of a socket is INADDR_ANY, meaning any local address on a
multi-homed host. A multi-homed host can use this option to accept
connections to only one of its addresses (in the case of a
ServerSocket or DatagramSocket), or to specify its return address
to the peer (for a Socket or DatagramSocket). The parameter of
this option is an InetAddress.

SO_BROADCAST

Sets SO_BROADCAST for a socket. This option enables and disables
the ability of the process to send broadcast messages. It is supported
for only datagram sockets and only on networks that support
the concept of a broadcast message (e.g. Ethernet, token ring, etc.),
and it is set by default for DatagramSockets.

IP_MULTICAST_IF

Set which outgoing interface on which to send multicast packets.
Useful on hosts with multiple network interfaces, where applications
want to use other than the system default. Takes/returns an InetAddress.

IP_MULTICAST_IF2

Same as above. This option is introduced so that the behaviour
with IP_MULTICAST_IF will be kept the same as before, while
this new option can support setting outgoing interfaces with either
IPv4 and IPv6 addresses.
NOTE: make sure there is no conflict with this

SO_LINGER

Specify a linger-on-close timeout. This option disables/enables
immediate return from a close() of a TCP Socket. Enabling
this option with a non-zero Integer timeout means that a
close() will block pending the transmission and acknowledgement
of all data written to the peer, at which point the socket is closed
gracefully. Upon reaching the linger timeout, the socket is
closed forcefully, with a TCP RST. Enabling the option with a
timeout of zero does a forceful close immediately. If the specified
timeout value exceeds 65,535 it will be reduced to 65,535.

SO_TIMEOUT

The option must be set prior to entering a blocking
operation to take effect. If the timeout expires and the
operation would continue to block,
java.io.InterruptedIOException is raised. The Socket is
not closed in this case.

SO_SNDBUF

Set a hint the size of the underlying buffers used by the
platform for outgoing network I/O. When used in set, this is a
suggestion to the kernel from the application about the size of
buffers to use for the data to be sent over the socket. When
used in get, this must return the size of the buffer actually
used by the platform when sending out data on this socket.
Valid for all sockets: SocketImpl, DatagramSocketImpl

SO_RCVBUF

Set a hint the size of the underlying buffers used by the
platform for incoming network I/O. When used in set, this is a
suggestion to the kernel from the application about the size of
buffers to use for the data to be received over the
socket. When used in get, this must return the size of the
buffer actually used by the platform when receiving in data on
this socket.
Valid for all sockets: SocketImpl, DatagramSocketImpl

SO_KEEPALIVE

When the keepalive option is set for a TCP socket and no data
has been exchanged across the socket in either direction for
2 hours (NOTE: the actual value is implementation dependent),
TCP automatically sends a keepalive probe to the peer. This probe is a
TCP segment to which the peer must respond.
One of three responses is expected:
1. The peer responds with the expected ACK. The application is not
notified (since everything is OK). TCP will send another probe
following another 2 hours of inactivity.
2. The peer responds with an RST, which tells the local TCP that
the peer host has crashed and rebooted. The socket is closed.
3. There is no response from the peer. The socket is closed.
The purpose of this option is to detect if the peer host crashes.
Valid only for TCP socket: SocketImpl

SO_OOBINLINE

When the OOBINLINE option is set, any TCP urgent data received on
the socket will be received through the socket input stream.
When the option is disabled (which is the default) urgent data
is silently discarded.

Method Detail

setOption

Enable/disable the option specified by optID. If the option
is to be enabled, and it takes an option-specific "value", this is
passed in value. The actual type of value is option-specific,
and it is an error to pass something that isn't of the expected type:

For an option that has a notion of on and off, and requires
a non-boolean parameter, setting its value to anything other than
Boolean(false) implicitly enables it.
Throws SocketException if the option is unrecognized,
the socket is closed, or some low-level error occurred

Parameters:

optID - identifies the option

value - the parameter of the socket option

Throws:

SocketException - if the option is unrecognized,
the socket is closed, or some low-level error occurred